Image transfer apparatus

ABSTRACT

An image transfer apparatus which comprises a platen (8) to which an image-forming material is to be attached and a transfer cylinder (1) to which an image receptor is to be attached, and which is for transferring an image formed in a photosensitive layer of an image-forming material to an image receptor by the introduction of the image-forming material and the image receptor into a nip formed by the platen and the transfer cylinder by the rotation of the platen and the transfer cylinder, the apparatus having an image-forming material attaching device comprising a device for holding the top end side of the image receptor to a platen surface along the entire width of the image receptor and a device for holding the bottom end side of the image receptor to a platen surface along the entire width of the image receptor, the device for holding the top end side being a pin bar (13) having pins protruded from an inside of a blanket (10) in a slope portion (12) continued from a partial cut-off portion formed in the platen.

TECHNICAL FIELD

The present invention relates to an image transfer apparatus. Morespecifically, it relates to an image transfer apparatus having a platenequipped with an image-forming material attaching device for improvingthe registering accuracy and stabilizing the registering, and a transfercylinder. Further, it relates to an image transfer apparatus having aplaten equipped with a means for facilitating the peeling of aprotection film from an image-forming material formed of a substrate, aphotosensitive layer and the protection film while the image-formingmaterial is attached to the platen, and a transfer cylinder.

TECHNICAL BACKGROUND

A single-color or multi-color prepress proof suitable for proofprinting, etch, is recently increasingly produced. The prepress proof isproduced by imagewise exposing an image-forming material comprising asubstrate and photosensitive layer formed on one surface of thesubstrate and then transferring an image to an image receptor such aspaper under heat, generally around 100° C. The image-forming material isformed of a substrate, a photosensitive layer formed on one surface ofsaid substrate and a protection film. As the substrate and theprotection film, a thin film or sheet formed from a material such ascellulose acetate, polystyrene, polyvinyl chloride or polyethyleneterephthalate is used. As the image receptor, a properly selectedprinting sheet such as paper or a film is used.

As an apparatus for preparing the above prepress proof, generally, therehas been proposed an image-transfer apparatus having a platen to whichan image-forming material is to be attached and a transfer cylinder towhich an image receptor is to be attached, and the platen and thetransfer cylinder are brought into contact so that a photosensitivelayer of the image-forming material and an image receptor are broughtinto contact with each other under pressure to transfer an image formedon the photosensitive layer to the image receptor in a nip portionformed by the platen and the transfer cylinder. A multi-color imagetransfer product or a prepress proof sheet is produced by color-scanningan original of multi-color image, imagewise exposing image-formingmaterials corresponding to separated colors, e.g., yellow, magenta, cyanand black to form images of these colors in the image forming materials,and consecutively transferring these formed images to one imagereceptor.

As a device for attaching the image-forming material to the platen, apin bar is generally used to facilitate the registering of each color.The pin bar has a structure in which a plurality of pins are provided ona plate extending in the axial-length direction of the platen. When,however, the pin bar is directly provided on the platen, there is causeda distinct height difference between the platen surface and the pin bar,and the image-forming material which has been attached has a nonuniformslackening. Therefore, the registering accuracy is insufficient in manycases. There is further another problem in that the area on which theprinting can be actually effected is decreased since the printing withsufficient registering accuracy cannot be carried out on the pin barportion.

For producing a multi-color prepress proof, a plurality of image-formingmaterials and one image receptor are used. After the imagewise exposure,each image-forming material is attached to the platen in a state inwhich the protection film is stacked. On the platen, the protection filmis manually peeled off by an operator. However, it is difficult to peeloff the thin protection film, and the peeling off the thin protectionfilm extremely impairs the workability. Further, when the protectionfilm is peeled off, an unexposed portion, i.e., an image portion, issometimes peeled together, and in such a case, no aesthetically fineimage transfer product can be obtained.

It has been strongly desired to develop a device for attaching asheet-like substance such as an image-forming material without causing afailure in registering and a device with which the protection film ofthe image-forming material can be easily peeled off. However, no devicewhich satisfies the above desire has been developed.

It is therefore an object of the present invention to provide an imagetransfer apparatus having a device with which the image-forming materialcan be attached to the platen without causing a failure in registering.It is further another object of the present invention to provide animage transfer apparatus having a platen equipped with a device foreasily peeling off the protection film of the image-forming material anda transfer cylinder.

DISCLOSURE OF THE INVENTION

The present invention provides an image transfer apparatus, whichcomprises a platen to which an image-forming material is to be attachedand a transfer cylinder to which an image receptor is to be attached,and which is for transferring an image formed in a photosensitive layerof an image-forming material to an image receptor by the introduction ofthe image-forming material and the image receptor into a nip formed bythe platen and the transfer cylinder by the rotation of the platen andthe transfer cylinder,

the apparatus having an image-forming material attaching devicecomprising a device for holding the top end side of the . .imagereceptor.!. .Iadd.image-forming material .Iaddend.to a platen surfacealong the entire width of the . .image receptor.!. .Iadd.image-formingmaterial .Iaddend.and a device for holding the bottom end side of the ..image receptor.!. .Iadd.image-forming material .Iaddend.to a platensurface along the entire width of the . .image receptor.!..Iadd.image-forming material.Iaddend.,

the device for holding the top end side being a pin bar having pinsprotruded from an inside of a blanket in a slope portion continued froma partial cut-off portion formed in the platen.

Further, the present invention provides an image transfer apparatushaving a means for peeling off a protection film, with which aprotection film can be easily peeled off from an image-forming materialformed of a substrate, a photosensitive layer formed on the substrateand the protection film stacked on the photosensitive layer while theimage-forming material is attached to the platen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an image transferapparatus used in the present invention.

FIGS. 2 and 3 are schematic cross-sectional views of image-formingmaterial attaching devices according to the present invention.

FIG. 4 is a schematic view of a platen having the means for peeling offthe protection film, provided by the present invention.

FIG. 5 is a schematic cross-sectional view of the means for peeling offthe protection film, provided by the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be detailed hereinafter with reference to theattached drawings.

The constitution of the image transfer apparatus used in the presentinvention will be explained below with reference to FIG. 1. FIG. 1 is aschematic cross-sectional view of the image transfer apparatus which hasa platen equipped with an image-forming material attaching device and towhich an image-forming material is to be attached and a transfercylinder to which an image receptor such as paper is to be attached,provided by the present invention

A surface of a transfer cylinder 1 is provided with a partial cut-offportion 2, and a clamp comprising a holder 3 and a holder seat 4, whichare means for attaching the top end side of an image receptor, and aclamp comprising a holder 5 and a holder seat 6, which are a means forattaching the bottom end side of the image receptor, are provided withinthe above partial cut-off portion. The holders 3 and 5 are provided withactuation shafts 7 on which the holders are actuated by a manual orelectric actuation means. The holders are allowed to open and close bythe rotation of the actuation means. The image receptor (not shown) suchas paper is attached to the transfer cylinder by holding it with the topend side clamp, rotating the transfer cylinder in an arrow directionwhile the image receptor is under tension, and then holding the imagereceptor with the bottom end side clamp.

The constitution of a platen 8 will be explained with reference toFIG. 1. The platen 8 is provided with a partial cut-off portion 9. Thesurface of the platen 8 is wrapped with a blanket 10, and the blanket 10is fixed within the partial cut-off portion with a blanket fixing means11. The partial cut-off portion 9 has slope portions 12 extendingbetween the partial cut-off portion and a platen surface(circumferential surface), and one slope portion is provided with a pinbar 13. The pin bar 13 is pressed on a platen surface by means of theblanket which has holes in places corresponding to pin positions of thepin bar 13. The pin bar 13 has such a height that its top does notprotrude over the circumferential surface of the platen 8. That isbecause the pin bar 13 or the surface of the transfer cylinder 1 are notdamaged in the rotation of the platen 8 and the transfer cylinder 1. Amagnet sheet 14 may be tiltably attached within the partial cut-offportion 9 for further securing the holding of the image-forming materialto the platen surface. An adhesive tape 15 is provided on a platensurface near the slope portion 12 where the pin bar 13 is located, andanother adhesive tape 15 is also provided on a platen surface near theother slope portion 12. The magnet sheet 14 is not so wide as to reachthe former adhesive tape 15 but is so wide as to cover the pin bar 13when the magnet sheet is tilted in the direction opposite to an arrow.The top end side of an image-forming material has holes corresponding topins of the pin bar 13. These holes are fit to the pins of the pin bar13, and the image-forming material is pressed with the magnet sheet 14.Then, the platen 8 is turned in the direction of the arrow, and the topend side and bottom end side of the image-forming material are fixed tothe surface of the platen with the adhesive tapes 15.

FIG. 2 shows the state in which the pin bar 13 is mounted. A first gagefilm 16 is placed on the platen surface. Then an elastic material 17 isplaced thereon, and a second gage film 18 is placed thereon. Then, thepin bar 13 is placed thereon, and a blanket having holes correspondingto pins of the pin bar is stacked. These elements are fixed to theplaten surface with the blanket fixing means 11 shown in FIG. 1, wherebythe pin bar 13 is fixed in place. FIG. 3 shows a state in which the pinbar is directly placed on the platen surface, and the first gage film,the elastic material, the second gage film and the blanket, all of whichhave holes corresponding to the pins of the pin bar, are consecutivelystacked.

As the gage films, a polyethylene terephthalate film is generally used.The gage film has the function of averaging the thickness variabilitywhen the blanket is used. The elastic material is generally formed of acork in an unwoven fabric state, and has the function of imparting theplaten surface with proper elasticity. The blanket is formed of alaminate prepared by stacking rubber layer(s) and cloth layer(s), and itis selected by taking elasticity and restorability into consideration.

FIG. 4 schematically shows a state in which means for peeling off theprotection film is provided on the platen. The means . .16.!. .Iadd.19.Iaddend.for peeling off the protection film is provided near the topend side of the image-forming material (not shown) attached to theplaten 8. In the means . .16.!. .Iadd.19 .Iaddend.for peeling off theprotection film, a hole is made in a predetermined place in the blanket10 as shown in FIG. 5, and a means for sticking to the substrate of theimage-forming material, such as an adhesive tape 20, is provided in thehole. For properly maintaining the height difference between the upperlevel of the blanket 10 and the sticking means, a projection portion 21may be provided within the hole of the blanket, and the adhesive tape 20may be attached to the upper surface of the projection portion. Theblanket is formed of a laminate prepared by stacking rubber layer(s),and cloth layer(s) and it is selected by taking elasticity andrestorability into consideration.

The function of the device for attaching the image-forming material,used in the present invention, will be explained hereinafter. The pinbar is fixed to the platen surface by means of the blanket, etc., and itcan be therefore easily attached and detached. Further, there is causedno distinct height difference between the pin bar and the platensurface, and the image-forming material can be therefore attached to theplaten with good registering accuracy. The positioning is accuratelycarried out by fitting the image-forming material having holes inpositions corresponding to the pin bar 13 to the pin bar, then theplaten 8 is rotated, and the image-forming material is attached to theplaten surface by means of the top end side adhesive tape and the bottomend side adhesive tape. Thereafter, the image-forming material ispressed to the means 19 for peeling off the protection film to make thesubstrate stick to the adhesive tape 20, whereby the protection film isfreed from the photosensitive layer formed on the substrate due to theheight difference between the surface of the adhesive tape 20 and thesurface of the blanket 10. The protection film can be easily peeled offby pulling the protection film.

INDUSTRIAL UTILITY

According to the present invention, there is provided an image transferapparatus which permits the facile attaching and detaching of the pinbar and which gives a multi-color prepress proof or an image transferproduct. According to the present invention, further, there is providedan image transfer apparatus which shows an improvement in workability infacile removal of the protection film from the image-forming materialand which gives an aesthetically fine prepress proof or an imagetransfer product without causing the peeling of an unexposed portion,i.e., an image portion.

We claim:
 1. An image transfer apparatus, which comprises a platen towhich an image-forming material is to be attached and a transfercylinder to which an image receptor is to be attached, and which is fortransferring an image formed in a photosensitive layer of animage-forming material to an image receptor by the introduction of theimage-forming material and the image receptor into a nip formed by theplaten and the transfer cylinder by the rotation of the platen and thetransfer cylinder,the apparatus having an image-forming materialattaching device comprising a device for holding the top end side of the. .image receptor.!. .Iadd.image-forming material .Iaddend.to a platensurface along the entire width of the . .image receptor.!..Iadd.image-forming material .Iaddend.and a device for holding thebottom end side of the . .image receptor.!. .Iadd.image-forming material.Iaddend.to a platen surface along the entire width of the . .imagereceptor.!. .Iadd.image-forming material.Iaddend., . .the device forholding the top end side being a pin bar having pins protruded from aninside of a blanket in a slope portion continued from a partial cut-offportion formed in the platen.!. .Iadd.the device for holding the top endside comprising a pin bar located between a blanket and a slope portioncontinued from a partial cut-off portion formed in the platen, the pinbar having pins protruding through the blanket.Iaddend..
 2. An imagetransfer apparatus according to claim 1, wherein the platen has asurface layer portion which is a laminate obtained by stacking a firstgage film, an elastic material, a second gage film and a blanket in thisorder, the pin bar is placed inside the first gage film or the blanketand pins project through a surface layer portion located outside a placewhere the pin bar are placed.
 3. An image transfer apparatus accordingto claim 1, wherein the image-forming material is formed of a substrate,a photosensitive layer formed on the substrate and a protection filmstacked on the photosensitive layer,at least one means for peeling offthe protection film is provided in a place in the platen correspondingto a place near a top end side of the image-forming material, and themeans for peeling off the protection film is provided with an adhesivetape in a hole made in the blanket and in a position inside a blanketsurface. .Iadd.
 4. An image transfer apparatus comprising a platen towhich an image-forming material is to be attached and a transfercylinder to which an image receptor is to be attached, and which is fortransferring an image formed in a photosensitive layer of animage-forming material to an image receptor into a nip formed by theplaten and the transfer cylinder by the rotation of the platen and thetransfer cylinder, the image transfer apparatus further comprising:aplaten surface on the platen and a slope portion that slopes inwardlyfrom the platen surface; a blanket covering the platen surface and theslope portion, the blanket having an outer surface; and an image-formingmaterial attaching device comprising a device for holding a top end sideof the image-forming material to the platen surface, said image-formingmaterial attaching device comprising a pin bar having pins extendingthrough the outer surface of the blanket. .Iaddend..Iadd.
 5. The imagetransfer apparatus of claim 4, wherein the pin bar is located betweenthe slope portion and an inner surface of the blanket, and the pins ofthe pin bar extend completely through the blanket. .Iaddend..Iadd.6. Theimage transfer apparatus of claim 4, wherein the slope portion iscontinued from a partial cut-off portion formed in the platen..Iaddend..Iadd.7. The image transfer apparatus of claim 4, wherein theplaten has a surface layer portion comprising a laminate of a first gagefilm, an elastic material, a second gage film and a blanket in thisorder, the pin bar is placed inside the first gage film or the blanketand pins project through a surface layer portion located outside a placewhere the pin bar is placed. .Iaddend..Iadd.8. The image transferapparatus of claim 4, wherein the image-forming material is formed of asubstrate, a photosensitive layer formed on the substrate and aprotection film stacked on the photosensitive layer, the image transferapparatus further comprising at least one means for peeling off theprotection film provided in a place in the platen corresponding to aplace near a top end side of the image-forming material, the means forpeeling off the protection film being provided with an adhesive tape ina hole made in the blanket and in a position inside a blanket surface..Iaddend.